In general, a liquid tank is disposed in a device such as a water purifier, a bidet, a humidifier, an ice maker, and the like, which uses a liquid such as water. A water level sensing apparatus is installed in the liquid tank in order to maintain a uniform level of a liquid such as water in the interior of the liquid tank. The water level sensing apparatus includes a mechanical water level sensing apparatus and an electronic water level sensing apparatus.
The mechanical water level sensing apparatus senses the water level of a liquid by detecting a change in a magnetic force when a float ascends or descends due to its buoyancy in the liquid. The mechanical water level sensing apparatus includes a reed switch, a hall sensor, a magneto-resistance (MR) sensor, and the like.
The electronic water level sensing apparatus includes a capacitance sensor or the like that senses the level of liquid by detecting a change in capacitance.
However, because the related art mechanical water level sensing apparatus requires the float to perform a mechanical operation, there is a possibility that its operation may be defective due to the mechanical structure of the float. In addition, the defective operation of the float may lead to a defective detection by a magnet, making it impossible to accurately measure the water level of the liquid within the liquid tank.
In addition, due to the characteristics of the mechanical structure of the mechanical water level sensing apparatus, debris such as slime may be encrusted on the float or on a float support structure, possibly hindering a magnetic force from being normally detected.
In addition, when the mechanical water level sensing apparatus is detached to remove the slime, it is, in actuality, difficult to remove the slime due to the mechanically complicated shape of the water level sensing apparatus, or much time may be required to clean the slime.
Also, the liquid tank of a water purifier is fabricated to have a smooth inner wall in order to prevent formation of scratches thereupon, thus minimizing the possibility of becoming dirty (i.e., preventing the inner wall from being covered with dirt). Also, if a structure is installed within the liquid tank, the structure would be inevitably covered with dirt in any event, therefore, structures within the interior of the liquid tank are avoided as much as possible in designing a water purifier.
Thus, an installation of the mechanical water level sensing apparatus having a complicated external appearance within the liquid tank would result in an easy collection of debris on the outer surface of the water level sensing apparatus, contaminating purified water. Also, in this case, the interior of the liquid tank and the water level sensing apparatus should be cleaned more frequently.
In addition, because the mechanical water level sensing apparatus has a complicated structure in which the float ascends or descends, or the float is fixedly coupled with the liquid tank, the size and unit fabrication cost of the water level sensing apparatus increase.
In addition, because the capacitance sensor is installed on an outer wall surface of the liquid tank, it easily malfunctions due to the influence of moisture or debris around the liquid tank.